Secondary batteries, especially lithium-ion (Li-ion) batteries, are extensively used in daily life. Due to their high energy density, specific energy, and low capacity fading rate, Li-ion batteries have become an indispensable component for the electric vehicle (EV) and hybrid electric vehicle (HEV) market. Nevertheless, Li-ion batteries are very sensitive to their working temperature. An extremely low temperature can substantially reduce the accessible energy that can be discharged from the batteries, and it can also trigger the process of lithium plating on the battery anodes during the charge sequence, which accelerates the capacity fading process and may engender safety issues such as internal short circuit. At a low temperature, the functionality of Li-ion battery powered devices is therefore negatively affected. For example, the range of an EV will be shortened, and the energy recovery is usually turned off; the cellphone can be automatically turned off; and the flash cannot be used on a digital camera. Consequently, a fast preheating technology is essential to the proper operation of a Li-ion battery energy storage system.
A qualified Li-ion battery preheating system should be able to detect the battery (or battery pack) temperature and preheat the battery (or battery pack) when the temperature is below the setting value, and it should ensure every battery in the battery pack is heated evenly with the maximum temperature difference within 5° C., thus extending the lifespan of the battery (battery pack). In addition, a preheating system that rapidly warm up the battery (or battery pack) with a high efficiency will further promote the application and development of the Li-ion battery powered devices in cold regions and countries.
To date, there are four main battery preheating systems: forced convection heating system, alternating current (AC) heating system, exterior resistor heating system, and built-in resistor heating system. Considering these individually, then forced convection and exterior resistor heating systems heat the battery from the surface, which takes a longer time for heating when the battery is thick. Comparatively, the AC and built-in resistor heating systems warm the battery internally. The AC heating system charge and discharge the battery (or battery pack) at high frequency to generate Joule heat to warm up the battery (or battery pack). However, it takes relatively longer time and results in the battery capacity fading over long-term usage. In recent years, a design that assembles heating resistor inside Li-ion battery has been invented, which could elevate the battery temperature from −30° C. to 0° C. in one minute. This design is very effective and efficient, but it requires that the design of the Li-ion battery be changed and is only applicable to pouch and prismatic Li-ion batteries and does not include cylindrical Li-ion batteries which have higher energy density storage. Further, battery design must factor this additional internal component into the design process.
Accordingly, it would be beneficial to provide designers of Li-ion battery devices with a method of rapidly and efficiently preheating the Li-ion battery without requiring that they limit themselves to specific Li-ion battery designs and manufacturers etc. Accordingly, a battery preheating method and system compatible with any Li-ion battery would be advantageous.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.